Dissipation of high frequency vibratory energy



SEECH Y?" Oct. 9, 1962 F. NEsH 3,058,015

DIssIPATIoN 0F HIGH FREQUENCY VIBRATORY ENERGY Filed May 5, 1960 Tlcl..L #layer a/(me/l/ ATTORNEYS United States Patent C) 3,058,015DISSIPATION F HIGH FREQUENCY VIBRATQRY ENERGY Florence Nesh, 164 HartSt., Brooklyn 6, N.Y. Filed May 3, 1960, Ser. No. 26,658 4 Claims. (Cl.S10-8.7) (Granted under Title 35, U.S. Code (1952), sec. 266) Theinvention described herein may be manufactured and used by or for theGovernment of the United States of America for governmental purposesWithout the payment of any royalties thereon or therefor.

This invention relates to the dissipation of vibratory energy and t-hetransducer therefor, and particularly for use with and in vehicles suchas missiles and other space vehicles.

In the journal Missiles `and Rockets for September 14, 1958, on page 7,`there occurs a statement that scientists have found that silent, highfrequency sounds given olf by large rocket space vehicle boosters mayinjure the health of launching crews, that since sounds have been foundto cause stomach ulcers and reproductive disorders in animals, effortswere being made to avoid this danger to the health of Ithe launchingcrews by the use of effective mufflers for the big rockets.

An object of this invention is to provide a simple, practical andrelatively inexpensive broad band transducer for effectively dissipatingthe vibratory energy normally given off by the space vehicles and theirboosters, in a manner that will avoid any danger to the health of thelaunching crews, which will not materially interfere with the usualhandling and launching of such vehicles, and which may be employed toreduce the effect of high frequency vibrations in other objects wheresuch vibrations are troublesome.

Other objects and advantages will be apparent from the followingdescription of one example of the invention, Iand the novel `featureswill be particularly pointed out hereinafter in connection with theappended claims.

In the accompanying drawing:

FIG. l is a perspective view of an element o-f electrostrictive materialthat may be used in connection with this invention; and

FIG. 2 is an elevation, in section, on a larger scale, with a schematiccircuit, illustrating one example of the invention. v

In the illustrated embodiment of the invention, yan electrostrictive orpiezoelectric transducer 1 is attached, in any suitable manner, to `awall 2 of a space vehicle or its booster, so that vibrations of the wallacting on the transducer will be converted in the transducer intoelectric energy in the form of electric currents. These created electriccurrents are passed through a utilization circuit 3 Where the electricenergy is dissipated. The transducer 1 is formed of a body 4 of anysuitable electrostrictve or piezoelectric material such as, for example,of quartz crystals, Rochelle salt crystals, ammonium dihydrogenphosphate crystals, and certain ceramic materials such las bariumtitanate, lead titanatelead zirconate, barium titanate with a smallamo-unt of lead titanate or calcium titanate, and tourmaline. Anyelectrostrictive material may :be used. This body 4 is preferably ofwedge shape with opposite, diverging faces 5 and 6 that carry electrodedlayers or coatings 7 and These coatings may be provided in any suitablemanner, one of which is by condensing vaporized metals such as gold orsilver upon the divergent faces of the body, or by painting thedivergent faces of the body with a silver paint and baking it. Theelectroded layers are usually applied after the body has been fired.Other methods of providing the electrode surfaces are by evap- Miceorating, electroplating, or electrodepositing the metal on the oppositedivergent faces. Barium titanate is gaining wide use as anelectrostrictive material, because i-t manifests large electrostrictiveeffects when its molecular electric dipoles are oriented by means of apolarizing voltage, and because it has a high dielectric constant andrelatively low impedance, resistance to moisture, ruggedness, ability tooperate over wide temperature ranges, is of low relative cost per unitsurface area, and can be easily produced in `a great variety of sizesand shapes. The body 4 with its electroded layers or surfaces ispolarized in a direction between the layers.

One of the divergent, electroded faces, such as 6, of the body 4 iscaused to abut, face to face and flat against a metal plate 9, such asof brass or copper, for example, which is secured in any suitable mannerto the wall 2 of the vehicle or its booster that vibrates. The platel 9may be secured to wall 2 by screws 10, and preferably also by a layer 11of adhesive or cement interposed between the pla-te 9 and wall 2. Thecement layer 11 provides a very secure contact between the abuttingsurfaces of plate 9 and wall 2. If there are air bubbles or air layersbetween the plates 9 and wall 2, it interferes with the response of thetransducer to the vibrations in wall 2, and the cement eliminates thepossibility of having such interposed air bubbles or air layers betweenplate 9 and wall 2.

Another metal plate 12 such as of brass or copper, for example, isdisposed face to face and fiat against the electroded surface or layer 7of the other divergent face 5 of body 4, and bodies 13 and 14 of asuitable insulating cement are disposed at the larger 4and smaller endsof the -body y4 and connect :the plates 9 and 12. These cement bodiesunite the plates 9 and 12 against separation and in confining rel-ationto the electrostrictive body 4, so that the plates 9 and 12 and body 4with its electroded layers 7 and 8 form a unit acting as thetransducer 1. Any suitable insulating cement may be used for the cementbodies 13 and 14 but the well-known epoxy and arylic types of cementsare useful for the cement bodies 13 and 14 and for the cement layer 11.

Circuit wires 15 4and 16 are electrically connected to plates 9 and 12.,respectively. Wire 15 includes in series therein a control switch 17 anda variable resistor 18, and one or more instruments or electricaldevices 19, 2t) and 21 may be connected in parallel or series with wires15 and 16 to complete the utilization circuit 3. The utilization circuitis carried by one of the plates 9 and 19 or by the wall 2. When themissile or vehicle, or its booster, having wall 2 is launched, the wall2 will vibrate at a very high frequency or emit ultrasounds, and suchvibrations will be |applied to the transducer 1 carried thereby. Thevibrations applied to the transducer will create electric currents inthe transducer, and such currents will vbe passed through theutilization circuit where the energy of such currents will be used up toadvantage or dissipated. The devices 19, 20 and 21 may be instruments ordevices used in connection with the flight of the missile `or vehicleand receive their operating current from the transducer, or the devices19, 20 and 21 may be `any devices to receive the currents from thetransducer and dissipate the electric energy.

The transducer body 4 may have opposite parallel, electroded faces, butsince the ultrasound or high frequency vibrations produced by themissile or vehicle or its booster may cover a broad spectrum or band offrequencies, the wedge-shaped body 4 `appears to be preferable, andresponsive to the broadest possible band of frequencies of thevibrations, since each area of a different thickness of body 4 willrespond best to a particular part of the frequency band, and togethercan be highly responsiveto a broad frequency band.L The particularelectrostrictive material selected for the body 4 will depend upon thetemperature and other conditions of expected use.

Barium titanate of uniform thickness responds to vibration frequenciesof more than one fundamental frequency, but when in wedge shape its bandof frequencies is excellent. y

Uutrasounds and very high frequency vibrations do not propagater in thesame way as audible sounds and vibrations, and do not go out in alldirections as a circular wave. There are few absorbente for ultrasoundsand vibrations in the same nature las for audible sounds. Most solidsand liquids are good ktransmission media for ultrasounds and vibrations,Air and vacuum` are the best dampers for ultrasounds, but their usepresents a,

. of the transducer, the mechanical forces so applied cause theproduction of a current in the transducer ofthe same frequency as thevibrations, if both are of one fundamentaly frequency. While all of thisvibration may not be converted into an electric current, none will leavethe system ,as ultrasound, and some will be reflected back and forthbetween the transducer body and the plate faces 9 and 12, and so belostin attenuation in the ma* terial of the body 4. -There will be some lossat each f interface of bonding materials and some conversion to heat.

damping of ultrasounds and high frequency vibrations in missiles andtheir boosters, the basic principles so employed may be applied broadlyto the damping of other response to a broad While this invention isprimarily applicable to the electrically insulating means securing saidmetal plates j in abutting relation to said opposite, divergent,electrod- 2. A transducer device which comprises an electroi. strictivebody of wedge shape with its broadest faces in cement isan epoxy cement.

ultrasounds and very high frequency vibrations, where other or usualmethods of damping are inadequate.

It will be understood that various changes in the details, materials,steps and arrangements of parts, which have been herein described andillustrated in order to explain the nature of the invention, may be madeby those skilled in the art within thep'rinciple andscope ofk theinvention, as expressed in the appended claims.

kI claim:

l. A transducer device sensitive to a wide band of vibrations fordissipating vibrations over a broad frequency band of a vehicle to whichit may be attached,

opposite divergent relationship and having said kfaces electroded, arigid metal plate disposed ilat against each electroded face ofwsaidbody and extending beyondfthe periphery of said body forming anoverlapping area, electrically insulating cement disposed between saidmetal plates lling the volume between saidoverlapping to which said bodyis subjected and dissipating its energy,

wherebywhcn one of said plates is attached to an object subject tovibration, much energy of said vibration over a broad frequencybandinfthe object will ber converted by said body into electric 'energyand the latter dissipatek ed in said utilization circuit.

3. `The transducer according to claim 2, wherein said 4.fThe transduceraccording to elaim`2, cement is arylic cement.

References Cited in the tile of this patentr j j UNITED STATES PATENTS fL2,261,791 i Bokovoy Nov. 4, 2,361,071 f Vang f ....i -..p Oct.,24,2,534,0065 De Lanoy etal. Dec. l2, 1950 2,661,622 y Severs Dec. 8, 19532,716,708 Bradfield Aug. 30, 1955 i 2,716,893 Birdsall Sept. 6, 19552,882,989 Bruel et al. Apr. 21, 1959 2,924,814 Simpson s Feb. 9, 19602,959,242 Mulller et al. Nov.-8, 1960 y.FOREIGNr PATENTS j y 473,636fGreat Britain Oct., 18, 1937v 931,689 Germany Q.. Aug. 16, 1955 OTHERREFERENCES Technical Paper on the Measurement of In-Flight VibrationUnder 4Environmental Extremes, by Warren kD. Hancock, given at the 5thAnnual I.S.A. Flight, In-

strumentation Symposium, ton, 6 pages.

May 1959, Seattle, Washingwhereiny said

